17.2.2 Satisfying a One-Argument Test

When using one of the functions in Figure 17–3, the elements E of a sequence S are filtered not on the basis of the presence or absence of an object O under a two argument predicate, as with the functions described in Satisfying a Two-Argument Test, but rather on the basis of a one argument predicate.

  assoc-if       member-if           rassoc-if          
  assoc-if-not   member-if-not       rassoc-if-not      
  count-if       nsubst-if           remove-if          
  count-if-not   nsubst-if-not       remove-if-not      
  delete-if      nsubstitute-if      subst-if           
  delete-if-not  nsubstitute-if-not  subst-if-not       
  find-if        position-if         substitute-if      
  find-if-not    position-if-not     substitute-if-not  

  Figure 17–3: Operators that have One-Argument Tests to be Satisfied

The element E_i might not be considered directly. If a :key argument is provided, it is a designator for a function of one argument to be called with each E_i as an argument, and yielding an object Z_i to be used for comparison. (If there is no :key argument, Z_i is E_i.)

Functions defined in this specification and having a name that ends in “-if” accept a first argument that is a designator for a function of one argument, Z_i. An E_i is said to satisfy the test if this :test function returns a generalized boolean representing true.

Functions defined in this specification and having a name that ends in “-if-not” accept a first argument that is a designator for a function of one argument, Z_i. An E_i is said to satisfy the test if this :test function returns a generalized boolean representing false.